There are two general categories of guides used in conjunction with an endless, flexible transmission medium: fixed guides and movable guides. When in use, the fixed guide is in sliding contact with the transmission medium, and prevents vibration and wobbling of the transmission medium. The movable guide is also in sliding contact with the transmission medium, and not only prevents vibration and wobbling, but also stretches the transmission medium to prevent transmission failure due to excess tension and excess loosening of the transmission medium.
A typical conventional guide 500 is shown in FIGS. 9 and 10. The conventional guide is described on page 1 of the specification of Japanese patent application No. 2002-293792 and depicted in FIGS. 3 to 6 of the drawings of that application. In the conventional guide, a thin skin layer 510b is formed on the slide rail 510, on which a transmission chain slides. The skin is formed over a core 510 composed of glass fiber-reinforced polyamide 66 resin. When the skin layer 510b wears, the guide must support the traveling chain with its core layer 510b exposed on the sliding surface. Glass fibers, released from the core by the action of the chain, generate an abrasive action, just as if an abrasive material were placed between the guide and the chain. The abrasive action of the glass fibers promotes wear of the guide.
Furthermore heat tends to accumulate not only in the skin layer of the slide rail 510, but also in the core layer 510a. The difference in thermal properties between the glass fiber reinforced polyamide 66 resin forming the core layer 510a, and the polyamide 66 resin forming the skin layer 510b, can cause thermal deformation between the skin layer 510b and the core layer 510a. If the difference in thermal properties is large, cracks are generated in layers 510a and 510b, and separation of these layers can occur. The strength of guide is also impaired by thermal deterioration.
An object of this invention is to solve the above-mentioned problems, and to provide a guide in which heat accumulation in the slide rail portion is suppressed, thermal deterioration is reduced, and smooth siding contact between the guide and the traveling transmission medium can take place over a long period of time.